Recently, there is known an automatic inter-vehicle control system (ACC: adaptive cruise control) or a collision avoidance system, which monitors the conditions, for example, ahead of a vehicle by a radar and performs throttle control and brake control according to the conditions. The radar used for these systems uses a high-frequency module capable of transmitting and receiving high-frequency signals such as of millimeter waves or microwaves.
The high-frequency module transmits, from an antenna, a signal generated by a transmitting circuit and allows a receiving circuit to receive, via the antenna, a signal that has been returned being reflected from a target. The receiving circuit compares a signal supplied from the transmitting circuit via the wiring of a substrate with the signal received via the antenna and detects, for example, the position of and the distance to the target.
If the signal generated by the transmitting circuit is transmitted to the receiving circuit by way of a space above the substrate without passing through the wiring of the substrate, some problems arise such as of impairing isolation, lowering detection accuracy in respect such as of the position of and the distance to a target, or generating ghost.
Patent Literature 1 describes a high-frequency module including a casing in which a substrate that is mounted with a transmitting circuit and a receiving circuit is housed, and the opening of the casing is covered up with a shield frame made of metal. The transmitting circuit is enclosed by the shield frame and a bulkhead made of metal extending from the shield frame toward the substrate. Opposite to the bulkhead intervened by the substrate, an elastic member is provided being sandwiched between the substrate and the casing. When the elastic member presses the substrate against the bulkhead, the ground wiring provided to the substrate is reliably brought into contact with the bulkhead. The shield frame and the bulkhead prevent the high-frequency signals generated by the transmitting circuit from leaking out of the shield frame and the bulkhead.